A known method of the kind referred to is described in GB-A-2032844. In particular reference is made to a liquid which sets to form a polymer being introduced into the cavity and the specification refers to suitable polymers being polyesters, vinyl polymers and epoxy resins. Although the use of epoxy resins is not discussed in detail in GB-A-2032844, reference is made to the addition of diluents to lower the viscosity of the polymer liquid in order to lower the viscosity of the liquid so that it can be suitably poured into the cavity.
Another known method similar to the kind referred to, but not disclosing the use of epoxy resins as a resin material, is described in WO 88/06096. In this known specification, methacrylate resin is referred to as the preferred resin material and fire-resistance is obtained by incorporating a wire mesh in the resin interlayer to retain the interlayer in a coherent form when it commences to melt when subjected to intense heat. In the preferred method of manufacture, the glazing assembly is tilted at an angle to the horizontal and the predetermined quantity of methacrylate resin is poured into the cavity between the spaced apart upper edges of the inclined glass panes. The inclined glazing assembly with the introduced methacrylate resin is then lowered to a substantially horizontal position and the weight of the upper glass panel squeezes the resin material between the glass panels so as to completely fill the cavity between the glass panels. A similar process, without any reference to the introduction of a wire mesh, is also disclosed in GB-B-2155856 although in this latter specification no claims are made to the process enabling the production of glazing products having improved fire-resistance.
It has now been found that epoxy based resin materials provide a far better fire resistance when incorporated as an interlayer between spaced apart glass sheets than an interlayer of methacrylate resin material. However epoxy based liquid resin materials are generally too viscous at normal operating temperatures of up to 25.degree. C. to spread naturally between large area glass panes, e.g. each typically up to a size of 3000 mm by 1630 mm, which are intended to be spaced apart only a small distance, e.g. typically no more than 2 mm, in the finished glazing product. However if a higher degree of fire resistance is required, the interlayer thickness can be increased up to approximately 12 mm or so for an unwired glazing product.
It is of course known to add diluents to epoxy based liquid resin materials to reduce their viscosity. However the addition of too much diluent reduces the fire-resistance of the resin material. Moreover, if the viscosity of the liquid resin material is too low or too high, air bubbles tend to become trapped between the glass panes. This is especially apparent when a wire mesh is additionally embedded in the resin material between the spaced apart glass panes.
It is an object of the present invention to provide a method of manufacturing a fire-resistant laminated glass by introducing between spaced apart glass panes an epoxy based liquid resin material having a suitable viscosity to enable it to flow and spread between the glass panes.